[转自]  http://blog.sina.com.cn/s/blog_5d5996d001012o07.html

其实手机在网络方面的的监听也比较重要，有时候我们必须实时监控这个程序的实时网络状态，android在网络断开与连接的时候都会发出广播，我们通过接收系统的广播就可以实现网络的监听，下面是代码---

onCreate的时候实例化 

//监听器
   private NetState receiver=new NetState();
   private IntentFilter filter=new IntentFilter();

 filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
  this.registerReceiver(receiver,filter);
  receiver.onReceive(this,null);

一个广播接收类-

private class NetState extends BroadcastReceiver{

  @Override
  public voidonReceive(Context arg0, Intent arg1) {
   ConnectivityManagermanager =(ConnectivityManager)con.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo gprs =manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
    NetworkInfo wifi =manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    if(!gprs.isConnected() && !wifi.isConnected())
    {
     
      AlertDialog.Builder ab=newAlertDialog.Builder(con);
   
     //设定标题
       ab.setMessage("网络连接断开，请检查网络");
       //设定退出按钮
  
     //网络设置按钮
       ab.setPositiveButton("确定", newDialogInterface.OnClickListener() {
      
      @Override
      publicvoid onClick(DialogInterface dialog, int which) {
       //TODO Auto-generated method stub
       dialog.dismiss();
       ShakeActivity.this.finish();
      }
     }).show();          
          
    }
     

  
  }
  
 }